1. Field of the Invention
The present invention relates generally to vehicle electrical systems, and specifically to electrical control actuation systems, electrical accumulators that interface with electrical control actuation systems, and related methods of managing electrical control actuation systems and installing electrical accumulators for electrical control actuation systems.
2. Description of Related Art
Aircraft aerodynamic control surfaces such as, for example, ailerons, flaps, rudders, etc., are moved to control the roll, pitch and yaw of an aircraft. Modern aircraft have traditionally used a combination of fly-by-wire control with a centralized high-pressure hydraulic system that is capable of moving the control surfaces by translating the hydraulic pressure produced by the hydraulic pumps into linear movement in the actuator. With the advent of “more electric aircraft,” the control of movement of the aerodynamic control surfaces has made the transition from a centralized continuously pressurized hydraulic system and fly-by-wire (“control-by-wire”) to a “power-by-wire” electrical system utilizing electro-hydrostatic actuators which generally include a series of individual flight control component actuators each including an electrical motor driving an individual hydraulic pump, and/or a series of individual flight control component actuators each including an electrical motor driving a mechanical extension. This transition to power-by-wire has created a flight control actuation system that has short periods of high peak electric power required by the flight control actuation system as well as short periods of high peak regenerative electric power that is placed back onto the aircraft flight control actuation system bus.
In order to achieve high flight performance characteristics, the flight control actuation system must be moved at high rates. In the power-by-wire systems, this high rate movement is achieved by exercising a motor or pump, which results in a high level of power required from the electrical bus in order to move the associated aerodynamic control surface. Because high-performance control of the aerodynamic control surfaces often requires electrical breaking to make a hard stop in response to control movements by the pilot, the motor will act like a generator for a short period of time which will then generate high levels of power that are resultingly translated back onto the aircraft flight control actuation system bus.
In hydraulically powered legacy aircraft, the issues involved with respect to providing high-performance control, i.e., high peak hydraulic fluid demand and high peak regenerative hydraulic fluid feedback, have been addressed by including a large hydraulic reservoir that can absorb or produce the hydraulic fluid associated with these peak events. On modern “more electric aircraft,” until now, there existed no device capable of both absorbing excess power and supplying such power for peak events. Instead, such types of problems have been at least partially addressed by incorporating into the “power-by-wire” flight control actuation systems an over sized generator having a power capacity sufficient to deliver the average amount of power required by the flight control actuation system as well as any anticipated transient power requirements, and through use of regenerative resistors. That is, the regenerative power produced by the flight control actuation system is not able to be absorbed by the generator, for example, due to backlash effects on the engine mounted accessory drive, and so, according to the state-of-the-art, such regenerative power must be dissipated (“burned off”) in regenerative resistors. Notably, these peak events can cause large voltage transients on the aircraft flight control actuation system bus, which may fall outside of the bus standard/capacity. Further, as the heat created by the regenerative resistors is I2R dependant, this could result in a requirement of the aircraft to deal with on the order of kilowatts of heat, typically dealt with via active cooling by a dedicated cooling loop on the aircraft, e.g., fuel, air, Polyalphaolefin (PAO), etc., which can lead to a requirement to have an even larger generator to power the cooling unit.
The oversized generator or generators add additional weight and volume requirements to the aircraft. Further, the regenerative resistors not only waste a potential source of power, but raise heat dissipation issues that must be dealt with. Recognized by the inventors, therefore, is the need for a bidirectional electrical accumulator capable of providing the high peak power needed by the flight control actuation system, and which can absorb the regenerative power produced by the flight control actuation system. Further, recognized by the inventors is the need for a bidirectional electrical accumulator capable of supply power above and beyond what the aircraft electrical system generator or other aircraft power supply device is capable of supplying, particularly when the aircraft is in flight.